Improvement of Light Extraction Efficiency in Flip-Chip Light Emitting Diodes on SiC Substrate via Transparent Haze Films with Morphology-Controlled Collapsed Alumina Nanorods

Seunghwa Baek, Gumin Kang, Dongheok Shin, Kyuyoung Bae, Yong Hyun Kim, Kyoungsik Kim

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

We demonstrate GaN-based flip-chip light emitting diodes (FC-LEDs) on SiC substrate achieving high extraction efficiency by simply attaching the optically transparent haze films consisting of collapsed alumina nanorods. Through controlled etching time of alumina nanorods, we obtain four types of films that have different morphologies with different optical transmittance and haze properties. We show that the light output power of the FC-LEDs with film, which has 95.6% transmittance and 62.7% haze, increases by 20.4% in comparison to the bare LEDs. The angular radiation pattern of the LEDs also follows the Lambertian emission pattern without deteriorating the electrical properties of the device. The improvement of light extraction is mainly attributed to the reduced total internal reflection (TIR) via efficient out-coupling of guided light from SiC substrate to air by collapsed alumina nanorod structures in the film. The high transparency of film and reduced Fresnel reflection via graded refractive index transition between the film and SiC substrate also contribute to the extraction enhancement of the device. We systematically investigate the influence of haze films geometrical or optical properties on the extraction efficiency of FC-LEDs, and this study will provide a novel approach to enhance the performance of various optoelectronic devices.

Original languageEnglish
Pages (from-to)135-141
Number of pages7
JournalACS Applied Materials and Interfaces
Volume8
Issue number1
DOIs
Publication statusPublished - 2016 Jan 13

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Aluminum Oxide
Nanorods
Light emitting diodes
Alumina
Substrates
Opacity
Optoelectronic devices
Transparency
Etching
Refractive index
Electric properties
Optical properties
Air

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Cite this

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title = "Improvement of Light Extraction Efficiency in Flip-Chip Light Emitting Diodes on SiC Substrate via Transparent Haze Films with Morphology-Controlled Collapsed Alumina Nanorods",
abstract = "We demonstrate GaN-based flip-chip light emitting diodes (FC-LEDs) on SiC substrate achieving high extraction efficiency by simply attaching the optically transparent haze films consisting of collapsed alumina nanorods. Through controlled etching time of alumina nanorods, we obtain four types of films that have different morphologies with different optical transmittance and haze properties. We show that the light output power of the FC-LEDs with film, which has 95.6{\%} transmittance and 62.7{\%} haze, increases by 20.4{\%} in comparison to the bare LEDs. The angular radiation pattern of the LEDs also follows the Lambertian emission pattern without deteriorating the electrical properties of the device. The improvement of light extraction is mainly attributed to the reduced total internal reflection (TIR) via efficient out-coupling of guided light from SiC substrate to air by collapsed alumina nanorod structures in the film. The high transparency of film and reduced Fresnel reflection via graded refractive index transition between the film and SiC substrate also contribute to the extraction enhancement of the device. We systematically investigate the influence of haze films geometrical or optical properties on the extraction efficiency of FC-LEDs, and this study will provide a novel approach to enhance the performance of various optoelectronic devices.",
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Improvement of Light Extraction Efficiency in Flip-Chip Light Emitting Diodes on SiC Substrate via Transparent Haze Films with Morphology-Controlled Collapsed Alumina Nanorods. / Baek, Seunghwa; Kang, Gumin; Shin, Dongheok; Bae, Kyuyoung; Kim, Yong Hyun; Kim, Kyoungsik.

In: ACS Applied Materials and Interfaces, Vol. 8, No. 1, 13.01.2016, p. 135-141.

Research output: Contribution to journalArticle

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AU - Shin, Dongheok

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AU - Kim, Yong Hyun

AU - Kim, Kyoungsik

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